This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Theta defensins are host defense peptides produced in the white blood cells of Old World monkeys (but not in chimpanzees or humans;see references below). In experiments performed in mice and rats, theta defensins facilitate clearance of bacteria in experimental infections, and also profoundly reduce the lethal effects of systemic inflammation (severe sepsis). Our long term goal is to determine the suitability of theta defensins as human therapeutics. Two adult chimpanzees will receive graded (increasing), intravenously administered doses of a naturally occurring theta-defensin RTD-1). The goal of these experiments are 1) to determine if there is any acute or subacute toxicity associated with the treatment, 2) to determine whether the administered protein elicits an antibody response in the chimpanzees, and 3) to determine whether other immunologic mediators (cytokines) are affected by the treatments.